1. Field of the Invention
This invention relates to a hydraulic braking pressure generating apparatus for a vehicle and a hydraulic brake device for a vehicle including the hydraulic braking pressure generating apparatus. Particularly, this invention pertains to a hydraulic braking pressure generating apparatus for a vehicle which regulates an outputted hydraulic pressure of a hydraulic pressure generator and which outputs a regulated hydraulic pressure in response to a braking operation force transmitted through a member functioning as a stroke simulator, and a hydraulic brake device for a vehicle including this hydraulic braking pressure generating apparatus.
2. Description of the Related Art
With respect to a hydraulic braking pressure generating apparatus for a vehicle, various apparatus are known. Particularly, a hydraulic braking pressure generating apparatus for a vehicle which includes a hydraulic pressure generator for generating a predetermined hydraulic pressure irrespective of operation of a brake operation member and for outputting the hydraulic pressure, a member applying a stroke to an input member in response to the brake operation force and functioning as a stroke simulator and a regulation valve for regulating the outputted hydraulic pressure of the hydraulic pressure generator in response to the brake operation force transmitted through the member and for outputting a regulated hydraulic pressure is disclosed, for example, in Japanese patent laid-open publication No. 52(1977)-101376 (Japanese patent publication No. 61(1986)-37140 and Japanese patent laid-open publication No. 58(1983)-110357.
In the apparatus disclosed in the Japanese patent laid-open publication No. 52(1977)-101376, one hydraulic brake circuit is connected to a primary pressure chamber which is positioned at a primary side of a double piston through a branch conduit. An accumulator is disposed at an end surface of a reinforced piston facing to a master cylinder and a separation wall is disposed between the primary pressure chamber and the accumulator. Further, the apparatus disclosed in the Japanese patent laid-open publication No. 58(1983)-110357 pertains to a tandem master cylinder and an auxiliary piston mechanism has an operation face for enabling a detecting of a reaction force of the braking pressure.
In the above prior apparatuses, in case of that a spring for urging the regulation valve toward its initial position is set in such a manner that a load at which the stroke simulator begins to contract is smaller than a load at which the regulation valve begins to move, the regulation valve begins to move after the movement of the input member with a predetermined distance, and then the regulation valve opens and the hydraulic braking pressure is outputted. Therefore, so called idle stroke is increased and a brake feeling deteriorates.
Alternatively, in case of that the load at which the stroke simulator begins to contract is larger than a spring load at which the regulation valve opens, the regulation valve opens and the outputted hydraulic pressure is increased with a predetermined level, and then the input member begins to move. Therefore, a stroke is hardly given to the brake operation member until the outputted hydraulic pressure is increased with the predetermined level and a brake feeling in this time is also not desirable.